The present invention relates in general to hydraulic damping devices, particularly for use in damping the movements of an artificial joint. The device is of the type which includes a hydraulic cylinder and piston unit defining an annular chamber between the inner wall of the cylinder and the piston for storing a hydraulic medium. The piston is provided with an annular shoulder which divides the storing chamber into two partial chambers each communicating via damping passages at each side of the shoulder with a recess within the piston so that the hydraulic medium may pass from one partial chamber into the other and vice versa.
In prior-art damping cylinder and piston units of this kind, the partial chambers in general are arranged one after the other in axial direction. Known is also to provide two cylinder spaces of variable volume, whereby the piston during its movement reduces the volume of the first space or partial chamber and the hydraulic liquid flows through a connecting conduit in the correspondingly enlarged second partial chamber. The first partial chamber has been provided with a piston biased by a resetting element to act on the hydraulic medium.
Such prior-art hydraulic damping cylinder and piston units require relatively large installation space, and therefore are unsuitable for many applications. For example, in spite of the fact that the movements of an artificial joint can be damped with advantage by the hydraulic damping device of this kind, the practical utilization of the latter in the artificial joint encountered considerable difficulties. For example, due to the considerable length of conventional damping cylinders, the artificial knee joint has reached too far in the calf part, thus causing a very disadvantageous construction. In particular, hitherto it was impossible to construct an artificial joint in a modular form, inasmuch as the latter presumes that the knee joint does not extend to the calf part but is exchangeably mounted.